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 A119833 Primes p such that 2*p#-1 is prime. 2
 2, 3, 5, 7, 17, 19, 37, 71, 79, 113, 857, 863, 16361 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE 2*2 - 1 = 3, 3 prime so a(1)=2; 2*2*3 - 1 = 11, 11 prime so a(2)=3; 2*2*3*5 - 1 = 59, 59 prime so a(3)=5. MATHEMATICA Module[{nn=900, pr, pl}, pr=Prime[Range[nn]]; pl=FoldList[Times, pr]; Select[ Thread[{pr, pl}], PrimeQ[2*#[[2]]-1]&][[All, 1]]] (* Harvey P. Dale, May 02 2018 *) PROG (Magma) [p:p in PrimesUpTo(4000)|IsPrime(2*&*PrimesUpTo(p)-1)]; // Marius A. Burtea, Mar 25 2019 (Python) from sympy import isprime, nextprime def afind(limit): p = 2 twoprimorialp = 4 while p <= limit: if isprime(twoprimorialp - 1): print(p, end=", ") p = nextprime(p) twoprimorialp *= p afind(1000) # Michael S. Branicky, Jan 08 2022 CROSSREFS Cf. A119834, A119835. Sequence in context: A059498 A247147 A158085 * A127049 A142885 A108547 Adjacent sequences: A119830 A119831 A119832 * A119834 A119835 A119836 KEYWORD nonn,more AUTHOR Pierre CAMI, May 25 2006 EXTENSIONS a(13) from Michael S. Branicky, Jan 08 2022 STATUS approved

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Last modified March 27 12:57 EDT 2023. Contains 361570 sequences. (Running on oeis4.)